A turbocharger may be cooled via one or more mechanisms. For example, a turbocharger may be cooled via air, water, oil or other fluid. As to lubricant cooling (e.g., oil, whether natural, synthetic, etc.), some tradeoffs exists. For example, if a carbonaceous lubricant reaches too high of a temperature for too long of a time (e.g., consider a time-temperature dependence), carbonization (e.g., also known as coke formation or “coking”), may occur. Coking can exasperate heat generation and heat retention by any of a variety of mechanisms and, over time, coke deposits can shorten the lifetime of a lubricated bearing system. As an example, coke deposits may cause a reduction in heat transfer and an increase heat generation, which may lead to failure of the bearing system.
To overcome coking, a turbocharger may be configured to improve lubricant flow. For example, a pump may pressurize lubricant to increase flow rates to reduce residence time of lubricant in high temperature regions. However, an increase in lubricant pressure can exasperate various types of lubricant leakage issues. For example, an increase in lubricant pressure of a bearing system can result in leakage of lubricant to an exhaust turbine, to an air compressor or both. Escape via an exhaust turbine can lead to observable levels of smoke while escape via an air compressor can lead to lubricant entering an intercooler, combustion chambers (e.g., combustion cylinders), etc.
As to lubricant leakage from a bearing system to an air compressor, the main driving force is often a pressure differential created between lubricant passages/cavities inside a center housing that houses a bearing system of a turbocharger and an air space behind a compressor wheel (e.g., a space defined by a backplate and a compressor wheel). When the pressure inside the center housing is more than the pressure in the space behind a compressor wheel, the pressure differential can drive lubricant from the center housing to the compressor. Where an intercooler is employed, lost lubricant can foul the intercooler, air passages, combustion chambers, etc., which can impact performance, longevity, etc.
Various technologies and techniques described herein are directed to deflectors, journal bearings, housings, assemblies, etc., which may improve turbocharger performance, longevity, etc.